Answer:
[tex]z= 5-2i[/tex]
Step-by-step explanation:
Start replacing!
[tex](x+iy) + 4i (x-iy) = -3+18i \\ x+iy +4ix -4i^2 y = -3 + 18i \\\\x + i (4x+y) +4y = -3 + 18i\\x+4y + (4x+y) i = -3 + 18i[/tex]
Now two complex numbers are equal if both the real and imaginary parts are equal, which gives you the system of equation [tex]\left \{x+4y=-3} \atop {4x+y=18} \right.[/tex]
Pick any method to solve it and you'll get [tex] x=5, y= -2 [/tex]
